1. Field of the Invention
The present invention relates to an optical disk device arranged such that a separation type optical head is used, which includes a fixed optical head and a movable optical head, and the movable optical head is driven in radial directions of a disk by a linear motor.
2. Related Background Art
A typical conventional optomagnetic disk device as a storage device exhibits such an advantage that the capacity is larger than that of a hard disk device, but has a defect in that response speed during information accessing is slow. This defect is derived from the fact that the optical head of the optomagnetic disk device is heavier than the magnetic head of the hard disk device, and a sufficient acceleration for speeding up accessing cannot be obtained. To cope with this, a so-called separation type optical head has been proposed, wherein, for obtaining a light-weight optical head, the optical head is separated into a fixed optical head unit including a laser light source and sensors and into a movable optical head unit including a mirror and a lens actuator to thereby reduce the weight of the movable optical head unit.
Further, for obtaining a much-lighter-weight optical head, a system also has been proposed, wherein fine tracking based on a galvano-mirror and a seek operation based on a linear motor are combined. In this system, a carriage of the movable optical head unit is restrained to approximately 6-7 grams, and the weight is considerably small. However, because of a double structure for mounting a focusing lens actuator on the carriage, the reduction in weight is not necessarily sufficient.
As described above, the conventional separation type optical head is separated into the fixed optical head unit and the movable optical head to remarkably reduce the weight of the movable optical head. However, the movable optical head unit is typically a combination of the carriage for performing the seek operation and the lens actuator for effecting the tracking/focusing operations. The movable optical head unit has a weight of approximately several tens of grams. Hence, there inevitably arises a defect that the acceleration of the hard disk device is not attained at all, and the response speed is slow.